<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
		
		<div class="box1"> js 要多练</div>
		
		
		<script type="text/javascript">
			
			var box1 = document.getElementsByClassName('box1')[0];
			
			box1.style.fontSize = '72px';
			box1.style.border = '2px solid blue';
			box1.style.width= "200px";
			box1.style.height = '200px';
			box1.style.borderRadius = '50%';
			
		</script>
	</body>
</html>
